Hypothalamic and telencephalic catecholamine content in the brain of the teleost fish, Pygocentrus notatus, during the annual reproductive cycle.

The catecholamines noradrenaline (NA), dopamine (DA), and adrenaline (A) were measured in hypothalamic and telencephalic extracts of the Venezuelan freshwater fish "caribe colorado," Pygocentrus notatus, at different stages of the reproductive cycle. The concentration of NA was found to be significantly higher in the telencephalon than in the hypothalamus, but that of DA was higher in the hypothalamus than in the telencephalon. Fluctuations depending upon the reproductive stage and environmental conditions occurred in both hypothalamus and telencephalon. In the hypothalamus, DA content was highest during the prespawning period (June) as compared to other periods of the cycle. Although the NA concentration was reduced during spawning there was no significant variation during any other period. DA concentrations in both telencephalon and hypothalamus showed a similar pattern of changes. In the telencephalon, NA levels increased between preparatory and prespawning periods but decreased sharply during spawning. No sex differences were observed in either area at any stage of reproduction.